Influence of roughness on in-vivo properties of titanium implant surface and their electrochemical behavior

This study proposed an electrochemical etching method to modify and control the surface roughness of G2 titanium, and the roughness effects on electrochemical behaviors were further verified by electrochemical impedance spectroscopy (EIS). Through electrochemical etching process within an electrolyte of 3.5 wt.% NaCl, the rough surface, big pits and cavities on titanium surface are suitable for the growth and fixity of bone cells and tissues. When the etched G2 titanium immersed in Hank's solution, bone-like compositions, including calcium and phosphorus of hydroxyl apatite, likely precipitate on such rough surface. For EIS study, the equivalent circuit for molding the rough G2 titanium immersed in the Hank's solution can be express as: (R0) + (C1//R1) + {C2//[R2 + (C3//R3)]}. The internal resistances of electrodes or load wire were simulated by a resistance, the characterizations of electron and charge transportation or diffusion between interfaces was simulated by a RC parallel circuit. It was found that the resistances of G2 titanium, transport wire and counter material appeared as ohmic impedance (R0). The other resistances of oxide film resistance (R1), hydroxyl apatite/electrolyte (R2), and hydroxyl apatite (R3) as the internal resistances. The interface capacitances include contact capacitance (C1), chemical capacitance (C2), and double-layer capacitance (C3).